This proposal is designed to prepare Dr. Nehal Parikh, a neonatologist with demonstrated research skills, to become a leader in performing methodologically strong clinical studies of perinatal brain injury in high-risk infants. We propose a comprehensive 5-year career development program involving: 1) Two important clinical studies of brain injury in extremely low birth weight infants: A) A prospective cohort study of quantitative (volumetric) magnetic resonance imaging (MRI) performed at or near term to predict neurosensory impairments at >= 18 months (a study evaluating the properties of quantitative MRI as a diagnostic test, the incremental predictive value over qualitative MRI and routine clinical predictors, and the predictive value of total and regional brain volumes); B) A randomized trial among ventilator-dependent infants (who are conventionally treated with high-dose dexamethasone) to assess whether low-dose hydrocortisone therapy prevents the reduced regional and total cortical volumes common among such infants. These studies will impart research skills in neurodiagnostic tests, neuroprotective strategies, and prognostic assessments for high-risk infants. The findings will be of great interest and pave the way for R01 funding by the end of K23 funding; 2) Intensive mentorship. The primary mentor is a neonatologist and epidemiologist (Jon Tyson, MD, MPH), who is experienced in studies of brain injury, a PI in the NICHD Neonatal Research Network, a PI in the NHLBI Clinical Research Curriculum, Director of the Center for Clinical Research and Evidence Based Medicine, and a dedicated and successful mentor. For the above studies, Dr. Parikh will also have prominent co-mentors in neurology (lan Butler, MD), developmental psychology and quantitative MRI (Robert Lasky, PhD), and neonatology and investigator training (Kathleen Kennedy, MD, MPH, Director, Master's Degree Program in Clinical Research). Dr. Tyson's Center and the Pediatrics Department will support these studies; 3) Master's Degree in Clinical Research (matriculated by Dr. Parikh in Sept. 2003). Courses (36 credit hrs) include Research Ethics, Advanced Biostatistics, and Advanced Epidemiology. His thesis will be a major publication from the above research. Institutional strengths include one of the largest populations of high-risk infants in the US, a strong perinatal research program (1 of only 8 centers in both the NICHD Maternal-Fetal and Neonatal Networks), a neonatal ICU supportive of clinical research (with the largest number of infants randomized in Network trials last year), and a well functioning follow up program. The proposed program will provide Dr. Parikh the research experience, dedicated mentorship, and necessary coursework to become a leader in clinical research addressing perinatal brain injury.